Liquid crystal display devices are used not only for large-sized television but also for small-sized display devices such as a display section of a portable phone, and the like. Although a liquid crystal display device of the conventionally used TN (Twisted Nematic) mode has a relatively narrow viewing angle, in recent years, liquid crystal display devices of a wide viewing angle are being produced, such as those in an IPS (In-Plane-Switching) mode and in a VA (Vertical Alignment) mode. Among such wide viewing angle modes, the VA mode is employed in many liquid crystal display devices, by its capability of achieving a high contrast ratio.
MVA (Multi-domain Vertical Alignment) mode is known as one type of the VA mode, which MVA mode forms a plurality of liquid crystal domains in one pixel area. In the liquid crystal display device of the MVA mode, an alignment controlling structure is provided on a side of at least one of a pair of substrates that face each other and have a vertical alignment liquid crystal layer be sandwiched between the substrates, on a side on which the liquid crystal layer is provided. The alignment controlling structure is, for example, a linear slit (opening) or rib (projecting structure) provided on an electrode. The alignment controlling structure causes application of an alignment controlling force from one or both sides of the liquid crystal layer, by which a plurality of liquid crystal domains (typically, four liquid crystal domains) having different alignment directions are formed, to achieve improvement in viewing angle characteristics.
A known disadvantage of the VA mode is that its display quality is remarkably different between the display quality from a front direction and the display quality from an oblique direction. In particular, with halftone display, when the displaying characteristics are adjusted to be appropriate when the display is seen from the front direction, the display characteristics such as color and gamma characteristic largely differ from those when the display is seen from the oblique direction. The optical axis direction of the liquid crystal molecules is in its molecule long-axis direction; during the halftone display, the optical axis direction of the liquid crystal molecule is angled to a certain degree with respect to a main surface of the substrate. If a viewing angle (direction from which the display is seen) is changed in this state and the display image is viewed from a direction parallel to the optical axis direction of the liquid crystal molecule, that is, if the display image is viewed from the oblique direction, the display characteristics would differ largely from the display characteristics of when the display image is viewed from the front direction.
More specifically, the display image viewed from the oblique direction looks whitish as a whole as compared to when the display image is viewed from the front direction. Such a phenomenon is called “excess brightness”. For example, in a case in which a human face is displayed, from the front direction, face expressions and the like of the human face is viewable without discomfort, whereas from the oblique direction, the face may look whitish as a whole, and subtle tone expressions of the skin may be viewed white out.
In order to improve such excess brightness, one pixel electrode is divided into a plurality of (typically, two) subpixel electrodes, to provide a plurality of (typically, two) subpixels in one pixel by having different electric potentials between the subpixel electrodes. With such a liquid crystal display device, tone characteristics of a subpixel is adjusted so that the display is not reduced in quality when viewed from the oblique direction as compared to the display quality when viewed from the front direction (see for example, Patent Literatures 1 to 3).
In the liquid crystal display device disclosed in Patent Literature 1, two subpixel electrodes are connected to different source wires via different switching elements, and are driven so that the electric potential of the two subpixel electrodes differ from each other. Such difference in the electric potential between the subpixel electrodes causes a difference in the voltages applied to the liquid crystal layer of the subpixels. As a result, the subpixels have different transmissivities, thereby allowing for achieving improvement in the excess brightness.
In the liquid crystal display device disclosed in Patent Literature 2, two subpixel electrodes correspond to different switching elements, and these switching elements are connected to different gate wires. The liquid crystal display device of Patent Literature 2 is driven so that the two subpixel electrodes have different electric potentials, by having a time in which the two gate wires are switched on differ at least partially.
Moreover, a liquid crystal display device disclosed in Patent Literature 3 includes, in addition to the two subpixel electrodes, storage capacitor wires corresponding to the subpixel electrodes, respectively, which storage capacitor wires directly or indirectly form a storage capacitor with their respective subpixel electrode. By having a different CS voltage be applied to the storage capacitor wire, the effective voltage applied to the liquid crystal layer changes. In the liquid crystal display device of Patent Literature 3, improvement in the excess brightness is achieved as such.
Japanese Patent Application Publication, Tokukai, No. 2006-209135 A (Publication Date: Aug. 10, 2006)
Japanese Patent Application Publication, Tokukai, No. 2006-139288 A (Publication Date: Jun. 1, 2006)
Japanese Patent Application Publication, Tokukai, No. 2004-62146 A (Publication Date: Feb. 26, 2004)